Control apparatus



Nov. 26, 1957 H. J. SMITH 2,814,740

- CONTROL APPARATUS Original Filed Feb. 28, 1955 60 r ENSITIVE 9 CONTROLRELAY 55 wmoms 1 3 I 57 I M 61 62 I LOCK 54 I WINDING l l L- ::/52

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HARVEY J. SMITH fizz/a4 ATTORNEY CONTROL APPARATUS Harvey J. Smith, St.Louis Park, Minn., assignpr to Min neapolis-Honeywell Regulator Company,Minneapolis, Minn, a corporation of Delaware Continuation of abandonedapplication Serial No. 490,7 35, February 28, 1955. This applicationFebruary 13, 1956, Serial No. 565,126

9 Claims. 01. 307 1s2 This application is a continuation of applicationSerial No. 490,735, filed February 28, 1955, now abandoned.

This invention relates to control apparatus comprising, in essence, acondition sensing circuit, wherein the sensing element is a phototube orsimilar low current device, operable without other electronic dischargedevices, to provide a constant pulsating check on the existence of thecondition once such condition has been initiated, and automatic shutdownof a control device when such condition ceases to exist, or when thepulsations are interrupted.

In the field of flame detection, there are, generally speaking, twoapproaches available to detect the presence or absence of a flame. Thefirst approach involves the use of a heat responsive device, such as abimetal thermostat, to detect the presence or absence of a flame. viceis dependable because there are no components to wear out or fail;however, it has the drawback that its response to a failure of flame maybe in the neighborhood of 90 seconds. This slow response feature isundesirable in such applications as gas furnace flame detectors, whereduring the 90 second response gap between no flame and a no flamesignal, a prohibitive amount of gas may be discharged into the furnacesetting up the possibility of explosion upon a re-ignition. The secondapproach is electronic. In such a system the presence or absence offlame is detected by a phototube or other low output signal device, anda signal of a few micro amperes is passed to an electronic dischargedevice operating as an amplifier, which amplifies the signal indicatingthe presence of a flame and passes this amplified signal to a relaywhich directly or indirectly governs the control device. This type ofsystem has an excellent response time of approximately 2 to 4 seconds,but has the disadvantage that electronic discharge devices aresusceptible to electrical and mechanical failure. A further drawback tothe electronic system is the relatively high cost such a systeminvolves.

The system of the present invention solves the problem of reliability,response, and cost by substituting for the electron discharge device ofthe electronic system mentioned above a supersensitive relay, such as isproduced by the Assembly Product Company, which is operable by a fewmicro amperes of current, and thus can be operated by a phototube orsimilar device, to close a circuit allowing the necessary current topass to a pulsating relay circuit which constantly checks the existenceof the signal from the phototube. By incorporating a checking circuit,provision is made to drop out the control device if the pulsating shouldstop due to either lack of a signal from the phototube, or a mechanicalor electrical failure in the system, which incapacitates the pulsing ofthe pulsating relay.

It is therefore an object of this invention to provide a controlapparatus for sensing a condition without the need of an electronicdischarge device.

A second object of this invention is to provide the above system with apulsing action and automatic shutdown of a control device upon a failureof the pulsing action.

Such a de- 2,814,740 Patented Nov. 26, 195'? ice Another object of theinvention is to provide a system with both rapid response andreliability.

A further object is to provide a system that is of a simple design andcircuitry, and of relatively low cost.

Other objects of the invention will be apparent from a consideration ofthe accompanying specification, claims and drawing in which:

Figure 1 is a schematic view of the condition sensing and pulsatingcircuit applied to a flame detector apparatus, and

Figure 2 is a partial schematic view of the circuit of Figure 1 showinganother form of a flame detector.

in Figure l, a main gas valve 10 is electrically operated by a normallydeenergized solenoid 11, which when energized allows the passage of fuelfrom an inlet pipe 12 to a connector 13 and thence to a gas burner 14.Pilot valve 15 is also electrically operated by a normally deenergizedsolenoid 16, which when energized by the closing of contacts 17 and 18of a bimetal thermostat 19 causes passage of fuel from the inlet pipe 12to a pilot valve inlet pipe 20, a pipe 21, and a pilot burner 22.Connected in parallel across the pilot valve 15 by means of conductors89 and is an ignition transformer 86, grounded at 87 and connected withan ignition electrode 88.

From an alternating current electrical power source, not shown, a powerlead 23 connects with one side of a primary winding 24 of a transformer25. Conductor 26 connects with power lead 23 at one extremity and has acontact 27 at its other extremity which engages contact 28 of a normallyopen switch 29 when said switch is closed. Lead 30 connects the switch29 with the solenoid 11. The other power lead 31 is connected to theprimary winding 24. Conductor 32, extending from a junction with powerlead 31, is connected to contact 17, so that when the contacts 17 and 18close, the thermostat 19 is placed in series with the solenoid 16 bymeans of a connection 33 and conductors 34, 35, and 35a. From solenoid16, lead 36 connects with primary lead 23.

From the junction of conductors 34 and 35, lead 37 connects to solenoid11, thereby placing solenoid 11 in parallel with solenoid 16, and thesolenoids 11 and 16 in series with the thermostat 19, all of which areconnected across the power supply, not shown.

Conductor 39 leading from a secondary winding 38 of the transformer 25,makes a junction with lead 41 and is then grounded at 42. Conductor 43leads from the other end of the secondary winding 38 to a capacitor 44,from which conductor 45 leads to a junction with leads 46 and 47. Lead41 is attached to a cathode element 48 of a rectifying phototube 49, soplaced that it can detect the existence of a pilot burner flame from thepilot burner 22. Lead 47 is attached to an anode 54E of the phototube49. In series with the secondary winding 38 is a resistor 51 and acrossthe secondary winding 33 is a capacitor 52. A resistor 53 is placed inseries with a control winding 54 of a sensitive relay 55. A lock winding56 is electrically connected to a normally open switch 57 having acontact 58 which is actuated by the control winding 54 when energized.Said switch 57 is additionally actuated by winding 56 when energized toincrease contact pressure. Contact 59 is attached to one end of lead 60,the other end being attached to relay winding 61, across which capacitor62 is placed. in series with the relay winding 61 and capacitor 62 is aresistor 63, which leads to switch 6'4, having a contact 65, whoseposition is controlled by relay winding 61. Contact 66 is attached toone end of lead 670, the other end of lead 67a being attached to lead67b, which in turn is connected to lead 670 which connects to a terminalof a source of direct current power 68. The other terminal of the directcurrent power source has a lead 69 connected thereto that makes ajunction with lead 70, from whence lead 70 connects to the junction ofthe lock winding 56 and control winding 54 of the sensitive relay 55.

interposed between the contact 66' and the direct current power source63 is a lead 73, connected to the junction of leads 67a and 67b, havinga resistor 74, and a contact 75 disposed at one extremity. Alsointerposed between the contact 66 and the direct current power source63, and connected to the junction of leads 67b and 670, is another lead76 having a capacitor 77, and which is connected to a switch 78 havingcontacts 79 and 86, whose position is controlled by relay Winding 61.Contact 81 is attached to lead 82 which is connected to a main gas valverelay winding 83, across which is placed a capacitor 84. Conductor 85connects the other side of the relay winding 83 and the capacitor 84with a direct current power terminal and direct current power source 68by means of lead 69.

Assuming the system is in the condition shown in the schematic view, theoperation thereof is as follows: As the contacts 17 and 18 close,thereby setting up a demand for heat, a circuit is closed and currentfrom the power leads 23 and 31 passes through the lead 32, contacts l7,l6 and 19, lead 34, lead 35, lead 35a, and lead 36, causing solenoid 16to open the pilot valve 15, thus allowing fuel to pass from the inletpipe 12 through the pilot valve inlet pipe 20, pilot valve 15, pipe 21,and pilot burner 22. The circuit closed by the thermostat contacts 17and 18 also passes current through the ignition transformer 86, by meansof conductors 89 and 90, thus allowing electrode 88 to ignite the fueldischarging from the pilot burner 22. Since the switch 29 is still open,solenoid 11 cannot be energized at this time. At the appearance of theflame, the phototube 49, which has a voltage impressed across it at alltimes from the secondary winding 38, passes a direct current signal fromthe cathode to the anode which is filtered by the capacitor 52. Thefiltered signal energizes the control winding 54 of the sensitive relay55, causing switch 57 to pull in, closing the contacts 58 and 59. Theclosing of the contacts 55 and 59 produces a closed lock circuit orloop, from which direct current from a direct current power source 68can charge capacitor 62 and flow through leads 69 and 70, lock winding56, switch 57, contacts 53 and 59, lead 60, relay winding 61, resistor63, switch 64, contacts and 66, and leads 67a, b and 6 back to thedirect current power source 68. The closing of contacts 58 and 59 alsocauses the charging of capacitor 62. This direct current flow throughthe lock winding 56 causes the switch contacts 58 and 59 to be heldtogether with enough pressure to allow the current necessary to energizerelay winding 61 to pass therethrough, and this action is independent ofenergization of control winding 54. As the current energizes relaywinding 61, switch 64 is raised breaking the contacts 65 and 66, andhence the lock circuit mentioned above is broken and the lock winding 56is deenergized. This returns the control of switch 57 to control winding54. Normally control winding 54 remains energized. However, should thephototube 49 fail to see light and thus send no signal to the controlwinding 54, this winding is deenergized and switch 57 opens. The openingof the circuit containing the lock winding 56 does not immediately causethe switch 64 to close, as the charge on capacitor 62 causes a currentfiow through relay winding 61 to continue, momentarily, itsenergization. However, when the capacitor 62 is discharged to such anextent that the current flow, and thus the energization, through therelay winding 61 can no longer hold the switch 64 open, the switch 64then drops out and closes, and the direct current circuit describedabove is once more closed, and the lockingrelay opening process isrepeated. The pulse repetition rate depends on the discharge rate ofcapacitor 62 and the continued signal to control winding 54 from thephototube 49.

A checking circuit, which includes a main gas valve relay winding 83, isincluded in the system and is comprised of the direct current powersource 68, leads 69 and 85, relay winding 83, capacitor 84, lead 82,switch 78, leads 73 and 76, capacitor 77, resistor 74, and leads 67b and670. The function of this circuit is to maintain the main gas valverelay winding 83 energized only if the phototube 49 passes a signal tothe control coil 54 causing its energization, and if the lock circuitcontinues to pulse, that is, if it continues to open and close. Thus ifthe lock circuit fails to pulse due to a mechanical failure, sticking ofcontacts, direct current power failure, etc., even though the phototube49 has passed a signal energizing the control coil 54, the main gasvalve relay winding 83 will be deenergized and the main gas valve lltlwill close, due to the opening of switch 29.

To achieve the function desired, it is necessary that the time constantof relay winding 61 and capacitor 62 be less than the time constant ofrelay Winding 53 and capacitor 84 to the extent that the relative timeconstants allow the relay 61 to be energized thereby breaking the lockcircuit, causing discharge of the capacitor 62 through relay winding61!, thereby reclosing the lock circuit in a space of time less than thetime required to fully discharge the capacitor 84. This condition isrequired so that capacitor S4- is never discharged to such an extentthat relay Winding 83 becomes partially or totally deenergized, so as toallow flutter or opening of switch 29 while relay winding 61 ispulsatingly being energized and deenergized.

With the thermostat 19 open and not asking for heat, the circuit is asshown and capacitor has no charge, as the charge it had when lastenergized has been dissipated through relay winding 83, while capacitor77 is fully charged by the direct current power source 68, thus allowingno current flow through the checking circuit under the circumstances.However, when the thermostat l9 asks for heat, with the consequentlighting of the pilot burner 22, the energization of the control coil 54closing switch 57, and the energization of relay winding 61, switch 78,which is under the control of relay winding 61, opens contacts 31 and'79 and closes contacts 75 and 80, making a circuit between resistor 74and capacitor 77, which causes a discharge of capacitor 77. This portionof the cycle causes a difference in potential between capacitors '77 and84 and the direct current power source 68 so that when a circuitcontaining all of them is re-established, due to the discharge ofcapacitor 62 and resultant deenergization of relay winding 61 with theconsequent movement of switch '78 reclosing contacts and 81, a currentwill flow in said circuit charging capacitors 77 and 84 and energizingrelay winding 83 thus closing switch 29 and thereby completing thecircuit containing solenoid 11. Solenoid 11 is then energized openingmain gas valve 10 and allowing fuel How to burner 14.

As long as the lock circuit continues to pulse, causing relay winding 61to be energized and then deenergized successively, as describedpreviously, thus moving switch 78 to successively and alternately openand close the set of contacts 75 and 8t) and the set of contacts 79 and81, causing, thereby, discharge of capacitor 77 when in series withresistance 74-, followed by charging of capacitors 77 and 84 when theyare in series, the relay winding 83 will remain energized and switch 29will remain closed. However, should the pulsating energization of relaywinding 61 cease, due to malfunctioning, and not due to failure of aphototube signal to the control winding 54,, and switch 64 remain eitheropen or closed, capacitor 84 will soon lose its charge to relay winding83. When switch 64 remains closed, relay winding 83 will becomedeenergized after capacitor 62 is discharged, as capacitor 77 willremain fully charged and thus no current can flow in the checkingcircuit. The deenergization of relay winding 83 causes switch 29 toopen, shutting down the main gas valve 10, as solenoid 11 is deenergizedthereby, and this even though the phototube receives light from thepilot burner 22 and passes a signal to the sensitive relay '5. If theswitch 64 should remain open, it is apparent no circuit would becompleted between the direct current power source 68 and the relaywinding as contacts 79 and 81 would remain open, thus switch 29 wouldopen as soon as the capacitor 84 were discharged to the point it couldno longer energize relay winding 83 to the extent necessary to holdswitch 29 closed.

It is of course apparent, that any failure of component parts such asthe phototube, sensitive relay, or break in the circuit, etc., stops thenecessary pulsing and therefore stops the main gas flow to the burner14.

In Figure 2, a secondary winding 38 of transformer has one side thereofconnected to capacitor 44 by means of conductor 43. To the other side ofcapacitor 44, a conductor 45 is attached which forms a junction withleads it; and 47. Lead 47 has a flame rod 91 at one extremity thereof.The other side of the secondary winding makes a junction with lead bymeans of conductor 39 and is thence grounded at 42. Ignition transformer86, grounded at 87, has electrode 88 extending therefrom as in Figure 1.Pilot burner 22 is placed proximately near electrode 88 and flame rod91.

Flame rod 91, when exposed to a flame from the pilot burner 22, passes asmall current through lead 47 to the sensitive relay, not shown, thusstarting the cycle described in conjunction with Figure 1.

It is obvious that modifications other than those described may be made.Therefore, the scope of the invention should be determined from thefollowing claims.

I claim:

1. In a condition detection system for a control device, a phototubeloop, a pulse locking loop, and a checking circuit; said phototube loopcomprising a rectifying phototube with an alternating current voltageimpressed thereon and a sensitive relay controlled by said phototube,said phototube being operable upon the occurrence of a predeterminedcondition to cause current passage in said phototube loop andenergization and closure of said sensitive relay; said pulse lockingloop having a direct current voltage impressed thereon and comprising afirst relay winding having a capacitor in parallel therewith, a normallyclosed switch operable by said first relay winding, and a lock windingfor said sensitive relay, said pulse locking loop being controlled bysaid sensitive relay such that closure of said sensitive relay causes aninstantaneous energization of said first relay winding and said lockingwinding; said checking circuit having a second switch operable by saidfirst relay winding and having a first loop with a resistor andcapacitor therein and a second loop having a direct current voltageimpressed thereon and having the capacitor of said first loop and asecond capacitor having a second relay winding in parallel therewith foractuating said control device, said first and second loops beingalternately opened and closed by said second switch.

2. In a condition detection system, the combination comprising aphototube loop and a pulse locking loop; said phototube loop comprisinga rectifying phototube with an alternating current voltage impressedthereon and a sensitive relay controlled by said phototube, saidphototube being operable when a predetermined condition exists to causecurrent passage in said phototube loop and energization and closure ofsaid sensitive relay; said pulse locking loop having a direct currentvoltage imressed thereon and comprising a relay winding having acapacitor in parallel therewith, a normally closed switch operable bysaid relay winding, a device having a resistance, and a lock winding forsaid sensitive relay; said pulse locking loop being controlled by saidsensitive relay so that closure of said sensitive relay causes aninstantaneous energization of said relay winding, said device, and saidlock winding.

3. In a flame detection system for a control device, a flame rod loop, apulse locking loop, and a checking circuit; said flame rod loopcomprising a rectifying flame rod with an electrical voltage impressedthereon and a sensitive relay controlled by said flame rod, said flamerod being operable when subjected to a flame to cause current passage insaid flame rod loop and energization and closure of said sensitiverelay; said pulse locking loop having a direct current voltage impressedthereon and comprising a first relay winding having a capacitor inparallel therewith, a normally closed switch operable by said firstrelay winding and a lock winding for said sensitive relay, said pulselocking loop being controlled by said sensitive relay such that closureof said sensitive relay causes an instantaneous energization of saidfirst relay winding and said lock winding; said checking circuit havinga second switch operable by said first relay winding and having a firstloop with a resistor and capacitor therein and a second loop having adirect current voltage impressed thereon and having the capacitor ofsaid first loop and a second capacitor having a second relay winding inparallel therewith for actuating said control device, said first andsecond loops being alternately opened and closed by said second switch.

4. In a flame detection system, the combination comprising: a flame rodloop having a rectifying flame rod with an electrical voltage impressedthereon and a sensitive relay controlled by said flame rod, said flamerod eing operable when subjected to a flame to cause current passage insaid flame rod loop and energization and closure of said sensitiverelay; and a pulse locking loop having a direct current voltageimpressed thereon, a relay winding having a capacitor in paralleltherewith, a normally closed switch operable by said relay winding, adevice having resistance, and a lock winding for said sensitive relay,said pulse locking loop being controlled by said sensitive relay so thatclosure of said sensitive relay causes an instantaneous energization ofsaid first relay winding, said device, and said lock winding.

5. In a control system, the combination comprising a condition sensingloop, a pulse locking loop, a checking circuit, and a control device;said condition sensing loop comprising a condition sensing electrondischarge device with an electrical voltage impressed thereon and asensitive relay controlled by said condition sensing electron dischargedevice, said condition sensing electron discharge device being operableon a condition to cause current passage in said condition sensing loopand energization and closure of said sensitive relay; said pulse lockingloop having a direct current voltage impressed thereon and comprising afirst electrically operated actuating means, a normally closed firstloop opening and closing means, said first actuating means causinginstantaneous movement of said first loop opening and closing means inone direction when energized but said first loop opening and closingmeans being delayed in movement in the opposite direction when saidfirst actuating means becomes deenergized, and an electrically operatedlocking means for said sensitive relay, said pulse locking loop beingcontrolled by said sensitive relay such that closure of said sensitiverelay causes an instantaneous energization of said first actuating meansand said locking means; said checking circuit having two loops inparallel, a second loop opening and closing means operable by said firstactuating means to alternately open and close each loop, said two loopscomprising a first resistive capacitance loop and a second loop having adirect current voltage impressed thereon and having the capacitance ofthefirst loop and a second electrically operated actuating means foractuating said control device, said second actuatin means having a timedelay means operable to maintain the actuated condition after thecessation of current flow of said second loop.

6. In control apparatus, the combination comprising a condition sensingloop and a pulse locking loop; said condition sensing loop comprising acondition sensing electron discharge device with an electrical. voltageimpressed thereon and a sensitive relay controlled by said conditionsensing electron discharge device, said condition sensing electrondischarge device being operable upon the occurrence of a condition tocause current passage in said condition sensing loop and energizationand closure of said sensitive relay; said pulse locking loop having adirect current voltage impressed thereon and comprising an electricallyoperated actuating means, a normally closed loop opening and closingmeans, said actuating means causing instantaneous movement of said loopopening and closing means in one direction when energized but said loopopening and closing being delayed in movement in the opposite directionwhen said actuating means is deenergized, a device having resistance,and an electrically operated locking means for said sensitive relay,said pulse locking loop being controlled by said sensitive relay so thatclosure of said sensitive relay causes an instantaneous energization ofsaid actuating means, said last named device, and said locking means.

7. in combination; a condition sensing loop and a pulse locking loop,said condition sensing loop comprising a condition sensing electrondischarge device with an electrical voltage impressed thereon and asensitive relay controlled by said condition sensing electron dischargedevice, said condition sensing electron discharge device being operableupon the occurrence of a condition to cause current passage in saidcondition sensing loop and energization and closure of said sensitiverelay; said pulse locking loop having a direct current voltage impressedthereon and comprising an electrically operated actuating means, anormally closed loop opening and closing means, said actuating meanscausing instantaneous movement of said loop opening and closing means inone direction when energized but said loop opening and closing meansbeing delayed in movement in the opposite direction when said actuatingmeans is deenergized, and locking means for said sensitive relay, saidpulse locking loop being controlled by said sensitive relay so thatclosure of said sensitive relay causes substantially an instantaneousenergization of said actuating means and said locking means.

8. In combination, a condition sensing loop, a pulse locking loop, achecking circuit, and a control device; said condition sensing loopcomprising a condition sensing device and a sensitive relay, saidcondition sensing device being operable upon the occurrence of acondition to cause current passage in said condition sensing loop andthereby energization and closure of said sensitive relay; said pulselocking loop having a voltage impressed thereon and comprising a firstelectrically operated actuating means, a normally closed first loopopening and closing means, said first actuating means causinginstantaneous movement of said first loop opening and closing means inone direction when energized but said first loop opening and closingmeans being delayed in movement in the opposite direction when saidfirst actuating means is deenergized, and locking means for saidsensitive relay, said pulse locking loop being controlled by saidsensitive relay so that closure of said sensitive relay causessubstantially an instantaneous energization of said first actuatingmeans and said locking means; said checking circuit comprising two loopsand including a second loop opening and closing means operable by saidfirst actuating means to alternately open and close each loop, a firstloop including an electrical energy storing means, and a second loophaving a voltage impressed thereon and including said electrical storingmeans and a second electrically operated actuating means having timedelay, said second electrically operated actuating means for actuatingsaid control device and operable to maintain for a time delay period theactuated condition after the cessation of current flow in said secondloop.

9. In combination, a condition sensing loop and a pulse locking loop;said condition sensing loop comprising a condition sensing means and asensitive relay, said condition sensing means being operable upon theoccurrence of a condition to cause current passage in said conditionsensing loop and thereby energization and closure of said sensitiverelay; said pulse locking loop having a voltage impressed thereon andcomprising an electrically operated actuating means, a normally closedloop opening and closing means, said actuating means causinginstantaneous movement of said loop opening and closing means in onedirection when energized but said loop opening and closing means beingdelayed in movement in the opposite direction when said actuating meansis de-energized, and locking means for said sensitive relay, said pulselocking loop being controlled by said sensitive relay so that closure ofsaid sensitive relay causes a substantially instantaneous energizationof said actuating means and said locking means.

No references cited.

